What does the idiom until you are blue in the face mean?

Answer 1

if you say something until you are blue in the face, you keep saying the same thing again and again but no one listens to you

One's face begins to change color when it begins to suffer from oxygen deprivation: usually turning towards a bluish color. Many strangulation victims end up with blue or even black faces for the same reason. This effect is used with exaggeration in Cartoons--frequently for characters unable or trying not to breathe.

The idiom "until you're blue in the face" means one is talking incessantly...and seemingly without even stopping for breath(this is the idea of the idiom: that one talks so much they forget to breathe, causing their face to lose oxygen and turn blue).
it means you have talked till you can't talk anymore...there is nothing else that can be said. Example she kept askingme for advice and I kept telling her the same thing till I was blue in the face.

Answer 2

If you talk until you're blue in the face, you've talked until you ran out of air. Your face turns blue when you're suffocating -- the meaning is that you've talked until you can talk no more and the other person is still not cooperating.